In a conventional excimer laser, a frequent problem is the formation of a contaminant film on the interior surfaces of the laser's windows. This film is typically caused by the accretion of metallic particulate contaminants such as nickel chloride from the laser's electrodes. These particulate contaminants become suspended within the gaseous interior of the laser and drift to the windows, where they accumulate and interfere with laser beam transmission. As a result, the laser's windows must be removed and either cleaned or replaced as often as once every two million laser pulses. With a laser pulse frequency of 300 Hz, this may require a 10- to 20-minute window replacement procedure every one to three hours. This procedure, which may also result in the loss of a significant amount of the expensive gas mixture contained within the laser, adds considerably to the cost of operation of the laser.